lwIP - A Minimal TCP/IP implementation - Wikia

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15 API REFERENCE 15.2 Buffer functions } /* refernce the string */ netbuf_ref(buf, string, sizeof(string)); /* do something with the netbuf */ /* [...] */ /* deallocate netbuf */ netbuf_delete(buf); 15.2.6 netbuf len() Synopsis int netbuf len(struct netbuf *buf) Description Returns the total length of the data in the netbuf buf, even if the netbuf is fragmented. For a fragmented netbuf, the value obtained by calling this function is not the same as the size of the first fragment in the netbuf. 15.2.7 netbuf data() Synopsis int netbuf data(struct netbuf *buf, void **data, int *len) Description This function is used to obtain a pointer to and the length of a block of data in the netbuf buf. The arguments data and len are result parameters that will be filled with a pointer to the data and the length of the data pointed to. If the netbuf is fragmented, this function gives a pointer to one of the fragments in the netbuf. The application program must use the fragment handling functions netbuf_first() and netbuf_next() in order to reach all data in the netbuf. See the example under netbuf_next() for an example of how use netbuf_data(). 15.2.8 netbuf next() Synopsis int netbuf next(struct netbuf *buf) Description This function updates the internal fragment pointer in the netbuf buf so that it points to the next fragment in the netbuf. The return value is zero if there are more fragments in the netbuf, > 0 if the fragment pointer now points to the last fragment in the netbuf, and < 0 if the fragment pointer already pointed to the last fragment. Example This example shows how to use the netbuf_next() function. We assume that this is in the middle of a function and that the variable buf is a netbuf. /* [...] */ do { char *data; int len; 23
15 API REFERENCE 15.2 Buffer functions /* obtain a pointer to the data in the fragment */ netbuf_data(buf, &data, &len); /* do something with the data */ do_something(data, len); } while(netbuf_next(buf) >= 0); /* [...] */ 15.2.9 netbuf first() Synopsis void netbuf first(struct netbuf *buf) Description Resets the fragment pointer in the netbuf buf so that it points to the first fragment. 15.2.10 netbuf copy() Synopsis void netbuf copy(struct netbuf *buf, void *data, int len) Description Copies all of the data from the netbuf buf into the memory pointed to by data even if the netbuf buf is fragmented. The len parameter is an upper bound of how much data that will be copied into the memory pointed to by data. Example This example shows a simple use of netbuf_copy(). Here, 200 bytes of memory is allocated on the stack to hold data. Even if the netbuf buf has more data that 200 bytes, only 200 bytes are copied into data. void example_function(struct netbuf *buf) { char data[200]; netbuf_copy(buf, data, 200); } /* do something with the data */ 15.2.11 netbuf chain() Synopsis void netbuf chain(struct netbuf *head, struct netbuf *tail) Description Chains the two netbufs head and tail together so that the data in tail will become the last fragment(s) in head. The netbuf tail is deallocated and should not be used after the call to this function. 15.2.12 netbuf fromaddr() Synopsis struct ip addr * netbuf fromaddr(struct netbuf *buf) 24
Page 1: Design and Implementation of the lw
Page 4 and 5: Contents 1 Introduction 1 2 Protoco
Page 6 and 7: 2 PROTOCOL LAYERING 1 Introduction
Page 8 and 9: 6 BUFFER AND MEMORY MANAGEMENT of l
Page 10 and 11: 7 NETWORK INTERFACES 6.2 Memory man
Page 12 and 13: 8 IP PROCESSING is set by the devic
Page 14 and 15: 10 TCP PROCESSING struct udp_pcb {
Page 16 and 17: 10 TCP PROCESSING 10.2 Data structu
Page 18 and 19: 10 TCP PROCESSING 10.5 Receiving se
Page 20 and 21: 11 INTERFACING THE STACK 10.9 Round
Page 22 and 23: 13 STATISTICAL CODE ANALYSIS 12.2 I
Page 24 and 25: 13 STATISTICAL CODE ANALYSIS 13.2 O
Page 26 and 27: 15 API REFERENCE 15 API reference 1
Page 30 and 31: 16 NETWORK CONNECTION FUNCTIONS Des
Page 32 and 33: 16 NETWORK CONNECTION FUNCTIONS Exa
Page 34 and 35: 16 NETWORK CONNECTION FUNCTIONS } /
Page 36 and 37: 17 BSD SOCKET LIBRARY 17.3 Connecti
Page 38 and 39: 17 BSD SOCKET LIBRARY 17.4 Sending
Page 40 and 41: 17 BSD SOCKET LIBRARY 17.4 Sending
Page 42 and 43: 18 CODE EXAMPLES 18.1 Using the API
Page 44 and 45: 18 CODE EXAMPLES 18.2 Directly inte
Page 46: REFERENCES REFERENCES References [A

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